Blood purification systems, which are used for conducting hemodialysis, hemodiafiltration or hemofiltration, involve the extracorporeal circulation of blood through an exchanger with a semi-permeable membrane. Such systems further include a hydraulic system for circulating blood and a hydraulic system for circulating replacement fluid or dialysate comprising the certain blood electrolytes in concentrations close to that of the blood of a healthy subject. Standard dialysis treatment, using an installed apparatus in hospitals, comprises two phases, namely, (a) dialysis, in which toxic substances and scoriae (normally small molecules) pass through the semi-permeable membrane from the blood to the dialysis liquid or dialysate, and (b) ultrafiltration, in which a pressure difference between the blood circuit and the dialysate circuit, more precisely a reduced pressure in the latter circuit, causes the blood content of water to be reduced by a predetermined amount.
Conventionally, a reservoir bag is provided for storing a dialysate which comprises filtered water mixed with a patient's prescription. In certain cases, the dialysate is required to be heated to a predefined temperature (usually the patient's body temperature) before being used. The reservoir bag is usually made of a thin plastic material comprising a liner which is capable of being heated without sustaining any damage or breakdown. The bag unfolds as it fills up with the dialysate and can be heated over a hot surface or any suitable heating device used in conjunction with a dialysis system.
In order to start heating the dialysate in the bag, there needs to be enough fluid in the bag for heat transfer to take place. Conventionally, a clinician takes a 6-liter container of tap water and mixes a patient's prescription, which may be in a powder form, with the tap water. The container is then shaken to mix the water and prescription well. The container usually is provided with a top connector which is connected to a dialysis system. The fluid mixture from the container is run through a sorbent for filtration and, once treated with the sorbent, the fluid mixture/dialysate passes into the reservoir bag. A bulk of the priming procedure time comprises waiting for the reservoir bag to begin to fill. When there is enough dialysate in the bag, the dialysate begins to heat until it reaches a predefined temperature (which may be a patient's normal body temperature, i.e. 37° C.).
A problem encountered with current reservoir systems is that the reservoir bag does not sit properly in a heating pan/device, when not filled to a near full capacity, as the bag does not start “inflating” until fluid fills it up. Hence, the time spent in filling the bag is added to the time required for preparing a dialysis system. Further, the bag must be filled on site, yet be made of a material that is thin enough so that it can be heated. While, in theory, one can remove the thermoform pan and heating element with the liner and then put it back, there are still challenges with the weight of the fluid, efficiently installing the bag, and providing the bag with a proper surface to rest on.
Hence, there is a need for a reservoir bag which can be rapidly heated without having to wait for the completion of dialysate filtration. There is a need for a bag and a method of using the same which would reduce the number of steps and, hence, the time required in preparing a dialysis system for performing dialysis.